Draft Plan Released for Gas Works Cleanup

Back in August, the city released a draft plan for the cleanup of Gas Works Park. At issue is arsenic in the groundwater under the play area on the east edge of the park, which is likely the result of leaks and spills harking back to the days when Gas Works was actually a gas works. Comments on this draft plan are being sought through October 10.

We first brought this upcoming work to your attention back in August of 2016. As we described, the work involves not only remediation of the groundwater contamination, but renovations to the play area facilities as well. As I wrote back in March, public comment was sought regarding a State Department of Ecology finding that the work would have no significant environmental effects. This was a relatively minor matter, it seems to me, but the plan before the public now is the main event.

The plan, produced by GeoEngineers located in downtown Seattle, would be carried out by the city in conjunction with Puget Sound Energy personnel and contractors, and work would commence this fall (after the comment period, I presume). The draft report runs to over 100 pages, and would require a competent… well, geoengineer, to thoroughly evaluate. If that’s not your cup of tea, I’ll try to save you the trouble here. Those interested in the details can find the full plan here. A cliff notes version is here.

A question in the minds of most park users is, “Will I still be able to use the park?” The answer is yes.

Initial phases of the work were completed in June of this year. This involved installation of a number of wells. A set of “injection wells” will be used to inject a reagent (ferrous sulfate) into the ground where it will combine with the arsenic to form a solid thereby preventing the migration of the arsenic into Lake Union and other places it ought not to be. The reagent comes in a solid form, and it needs to be mixed with water to achieve a desired concentration and to put it in liquid form for injection. This mixing will be done onsite by special staff trained to handle ferrous sulfate and per the terms of a health and safety plan. You may see a number of trucks during the injection phase which carry the portable pumping equipment. The injection phase is expected to last 1 to 2 weeks.

Is it safe? There seems to be little potential for any immediate harm coming to park users (although there is quite a bit of detail in the draft proposal concerning mixing of the reagent). But the larger question is how the ground water might be affected by injection of the reagent. And this must be weighed against the dangers posed by leaving the arsenic where it is. (You don’t hear too many good stories that involve arsenic.) A number of monitoring wells are in place to sample the ground water and measure parameters such as dissolved oxygen, oxidation potential, pH and temperature. These will be compared against baseline measurements taken prior to injection to be sure ground water quality is not being adversely affected.

Following the injection phase, the play area facilities will be renovated. This renovation will involve construction of new restrooms, repair and upgrading of the playground equipment, and upgrading of the facilities to meet ADA standards among other improvements.